Date: Sat, 31 Jan 2015 17:36:21 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Eric Badger <eric@badgerio.us> Cc: freebsd-current@freebsd.org Subject: Re: Filepaths in VM map for tmpfs files Message-ID: <20150131153621.GH42409@kib.kiev.ua> In-Reply-To: <54CCEFAB.9040406@badgerio.us> References: <54CCEFAB.9040406@badgerio.us>
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On Sat, Jan 31, 2015 at 09:07:23AM -0600, Eric Badger wrote:
> In FreeBSD 9, examining the VM map of a process (with e.g. 'procstat
> -v') with a tmpfs file mapped showed a VNODE type and displayed the file
> path. In 10.0 up to CURRENT (I believe this started at r250030), instead
> SWAP is shown without a filepath.
>
> This has some unfortunate consequences; I discovered this problem when
> trying to use dtrace's pid provider, which fails to find symbols for
> executables running from tmpfs.
>
> I've attached a patch which will repair procstat/dtrace. There are a few
> other places such a patch would be needed. I'm willing to put together
> such a patch, but would like to first hear some feedback that this seems
> like a reasonable approach, or if there's anything I've missed.
>
> Thoughts?
>
> Eric
>
>
> Index: sys/kern/kern_proc.c
> ===================================================================
> --- sys/kern/kern_proc.c (revision 277957)
> +++ sys/kern/kern_proc.c (working copy)
> @@ -2337,6 +2337,11 @@
> break;
> case OBJT_SWAP:
> kve->kve_type = KVME_TYPE_SWAP;
> + if ((lobj->flags & OBJ_TMPFS) != 0)
> + {
> + vp = lobj->un_pager.swp.swp_tmpfs;
> + vref(vp);
> + }
> break;
> case OBJT_DEVICE:
> kve->kve_type = KVME_TYPE_DEVICE;
First, shouldn't the kve_type changed to KVME_TYPE_VNODE as well ?
Second, note that it is possible that the vnode is recycled, so
OBJ_TMPFS flag is cleared for tmpfs swap object. The OBJ_TMPFS_NODE
flag is still set then. I am not sure what to do in this case,
should the type changed to KVME_TYPE_VNODE still, but kve_vn_*
fields left invalid ?
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